共查询到20条相似文献,搜索用时 15 毫秒
1.
《Materials Letters》2007,61(8-9):1633-1636
Nanocrystalline and well dispersed barium strontium titanate (BST) powders were prepared by a novel and simple citrate precursor method. This method involved direct crystallization of a white precursor from a stable solution in the citric acid (CA)–ethylene glycol (EG)–tetrabutyl titanate–M2+ (M = Ba, Sr) system under a specific pH value range. Subsequent heat treatment of the precursor at 850 °C led to a pure phase BST powder. TG/DTA was used to examine the decomposition behaviour of the precursor. The crystalline phase and morphology of the BST powders were investigated by XRD and TEM. It was found that the BST powders synthesized by citrate precursor process were more homogeneous and uniform than that obtained by the citrate gel method. 相似文献
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An oxalate route for the production of BaTiO3 has been modified to incorporate Mn (upto 2%) as a dopant and the reaction sequence has been studied. The resulting Mn-doped
BaTiO3 exhibits a dielectric constant with an increasing insensitivity to temperature and applied a.c. field as the Mn content is
increased. These samples possess a high electrical resistivity even after treatment in hydrogen at 1100°C and are therefore
suitable as dielectric for multilayer capacitors with base metal electrodes. 相似文献
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A simple soft chemical method of synthesizing barium titanate nanopowders and nanorods is described here, where titanium dioxide/titanium isopropoxide was taken as a source of titanium, tartaric acid was taken as a template material, nitric acid as an oxidizing agent. The synthesized powders and rods were characterized by XRD, TG and DTA, SEM and IR spectroscopy. In this process phase pure barium titanate nanopowders and nanorods can be prepared at a temperature of 900 °C and the process is simple and cost-effective. 相似文献
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Sung-Oong Kang Hoon-Sik Jang Bae Ho Park Yong-Il Kim 《Materials Research Bulletin》2008,43(4):996-1003
Single-crystal barium titanate (BaTiO3) nanorods were synthesized by a hydrothermal reaction using precursors of potassium titanate (K2O·nTiO2, n = 4 or 6) nanostructures. The precursors of potassium tetratitanate (K2Ti4O9) and potassium hexatitanate (K2Ti6O13) nanostructures were prepared by a sol-gel method in which a growth of K2O·nTiO2 (n = 4 or 6) nanorods was induced by a role of pre-crystallized K2O phase at defined heating temperatures. The specific morphologies of BaTiO3 nanorods featured with flat or stepped surfaces and rectangular or polygonal cross-section, were obtainable by selecting the structure of precursors. 相似文献
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Wanping Chen 《Materials Letters》2007,61(16):3378-3380
Perovskite Ba0.7Sr0.3TiO3 nanorods were synthesized in Triton X-100 reverse microemulsion at room temperature and characterized by XRD, ICP-AES, ED and TEM. The Ba0.7Sr0.3TiO3 nanorods with a diameter of 60-100 nm and a length of 450-1200 nm showed a single-crystalline tetragonal structure. The size of nanorods was effectively tuned by changing w value (molar ratio of water to surfactant), aging time and reactant concentration. 相似文献
8.
Wenxing Zhang Lixin Cao WenWen Wang Ge Su Wei Liu 《Journal of Materials Science: Materials in Electronics》2013,24(7):2234-2239
(Ba0.8Sr0.2ZryTi1?yO3) (y = 0.05, 0.1, 0.15 and 0.2) nanosized powders is synthesized by solvothermal method. The formation of (Ba0.8Sr0.2ZryTi1?yO3) was confirmed by XRD, FT-IR and XPS analysis. The purity of the (Ba0.8Sr0.2ZryTi1?yO3) was examined using FT-IR spectroscopy. The X-ray analysis proves that all as-synthesized Ba0.8Sr0.2ZryTi1?yO3 powders have a cubic perovskite structure. The surface characterization indicates the powder contains Zr and Sr elements. SEM investigation shows that the average particle size is reduced with increasing the Zr content and the average particle size is in the range 37–50 nm, the well dispersed nano powders have narrow particle size distribution. The study of dielectric properties shows that the Curie peaks of dielectric constant become broader and shift towards lower temperature on the basis of Ba0.8Sr0.2TiO3 and the dielectric loss decreases with increasing Zr content. 相似文献
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D.M. Schleich C. Derrington W. Godek D. Weisberg A. Wold 《Materials Research Bulletin》1977,12(4):321-326
Single crystals of barium titanate and members of the series BaTi1?xFexO3?xFx have been grown from a potassium fluoride flux. These crystals were made conductive by heating in a sealed evacuated silica tube in the presence of freshly ground titanium. Electrical, optical and magnetic measurements were performed in order to characterize these crystals. Optical measurements indicated a decrease in the band edge from 3.2(1) eV for barium titanate to 2.8(1) eV for Bati1?xFexO3?xFx(x = 0.02, 0.05, 0.07, 0.10). The photoelectrolytic behavior of reduced barium titanate was strongly quenched upon the substitution of iron and fluorine. 相似文献
12.
Synthesis of nm-sized barium titanate crystallites using a new LTDS method and their characterization 总被引:2,自引:0,他引:2
A new LTDS method was established to synthesize nm-sized barium titanate crystallites with particle sizes around 10 nm. This LTDS method was the following two features, i.e., (1) a heat of neutralization in a neutralization reaction between strong acid and base can be used as a driving force for a formation of barium titanate, and (2) barium titanate crystallites can be directly synthesized from Ti and Ba ions, not via intermediates. Therefore, using the LTDS method, it can be expected that there is no minimum limit in particle sizes, and also no contamination in barium titanate crystallites. At first, optimum conditions for a formation of barium titanate were screened at various reaction temperatures and Ba/Ti atomic ratios in the starting materials. As a result, the formation of barium titanate was found at higher reaction temperatures than 50°C and higher Ba/Ti atomic ratios than 5. Under a constant temperature, particle sizes decreased with increasing Ba/Ti atomic ratios while under a constant Ba/Ti atomic ratio, particle sizes were independent of reaction temperatures. Finally, barium titanate crystallites with particle sizes below 10 nm were first prepared. These particles were also characterized using various methods. 相似文献
13.
S.R. Dhage 《Materials Research Bulletin》2004,39(13):1993-1998
A simple citrate gel route was adopted for the preparation of bismuth titanate (Bi4Ti3O12) powders. Stoichiometric quantities of BiCl3 and TiOCl2 were mixed with required amount of citric acid, and the mixture was heated on a water bath. This leads to formation of gel, which was decomposed at 673 K. Formation of bismuth titanate was observed on calcining powders at 973 K by X-ray diffraction studies. The average particle size is found to be 20 nm by microscopy. The room temperature dielectric constant is found to be 175 at 1 kHz. The hysteresis loop parameters were also obtained by home built Sawer-Tower circuit. 相似文献
14.
《Advanced Powder Technology》1999,10(1):37-50
Crystalline, spherical barium titanate fine powders with a narrow particle size distribution were prepared by ultrasonic spray pyrolysis. The stability of the starting solution was influenced by type of barium source and peptizer. The particle structure was influenced by the pyrolysis temperature of the barium source. The particle structure derived from barium acetate was dense, while powders derived from barium nitrate involved a lot of hollow particles. As-prepared powders were crystallized to a perovskite structure. Inductively coupled plasma analysis showed that the BaO/TiO2 molar ratio of as-prepared powders was 50.5:49.5. The effects of the concentration of the starting fluid, pyrolysis temperature and flow rate of carrier air through the furnace on powder characteristics such as particle size, size distribution and crystal phase were investigated. The particle size depended on the concentration of starting solution and the flow rate of carrier air, but the particle size distribution was independent of these variables. Single-phase BaTiO3 was obtained at more than 700°C. The relative density of barium titanate sintered at 1200°C was 98%. The hollow particles in the powders resulted in a low sintering density and a large grain size. The dielectric constant and tan δ of barium titanate at 25°C were 4500 and 0.02, respectively. 相似文献
15.
In this research, a modified, cost effective sol-gel procedure applied to synthesize BaTiO3 nanoparticles. XRD and electron microscopy (SEM and TEM) applied for microstructural characterization of powders. The obtained results showed that the type of precursors, their ratio and the hydrolysis conditions had a great effect on time, temperature and therefore the costs of the synthesis process. By selection, utilization of optimized precursor's type, hydrolysis conditions, fine cubic BaTiO3 nanoparticles were synthesized at low temperature and in short time span (1 h calcination at 800 °C). The proposed procedure seems to be more preferable for mass production.The result indicated that the polymorphic transformation to tetragonal (ferroelectric characteristic) occurred at 900 °C, which might be an indication of being nanosized. 相似文献
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Satoshi Wada A. Nozawa M. Ohno H. Kakemoto T. Tsurumi Y. Kameshima Y. Ohba 《Journal of Materials Science》2009,44(19):5161-5166
Barium titanate (BaTiO3) nanocube particles below 20 nm were prepared by solvothermal method. A selection of organic solvent and inorganic materials
of Ba and Ti sources was most important for the preparation of nanocubes. A nucleation and particle growth of BaTiO3 nanoparticles led to a formation of the BaTiO3 nanocubes with a size of 10–15 nm at temperatures above 200 °C. 相似文献
18.
The barium titanyl oxalate, which was the precursor of barium titanate, was prepared by homogeneous precipitation using the diethyl oxalate as a precipitating agent. The oxalate dried at 80 °C was the crystalline phase, which was converted to amorphous-like phase after drying at 120 °C. The weight loss of oxalate was 47.3 wt%. The chemical formula of the oxalate could correspond to BaTiO(C2O4)2 · 4H2O. The barium titanate obtained from the calcination of oxalate at 850 °C was a tetragonal phase with a particle size of 0.2 m. 相似文献
19.
Jon F. Ihlefeld William J. Borland Jon-Paul Maria 《Journal of Materials Science》2008,43(12):4264-4270
Barium titanate stannate (BaTi1−x
Sn
x
O3, 0 ≤ x ≤ 0.25) thin films were deposited directly on copper foil substrates via a chelate chemical solution process. The films were
subsequently crystallized in a reducing atmosphere such that substrate oxidation was avoided and that the 2-valent state of
tin could be stabilized. Despite the stabilization of the low-melting temperature SnO oxidation state at high temperatures,
the final grain size was smaller with increased tin incorporation similar to other B-site substituted BaTiO3 films. Temperature and field-dependent dielectric measurements revealed a reduction in dielectric constant and dielectric
tuning with increasing tin concentration. The reduction in permittivity with reduced grain size is consistent with the well-known
trends for ceramic barium titanate and in combination with a defect-dipole model involving Sn acceptors, can be used to explain
the experimental trends. Phase transition frequency dependence was studied and for compositions containing up to 25 mole percent
tin. No phase transition dispersion was observed and thus no strong evidence of relaxor-like character. The phase transition
became increasingly diffuse with deviation from Curie–Weiss behavior, but the observed transition temperatures agreed well
with bulk reference data. 相似文献
20.
Chaoliang Mao Xianlin Dong Tao Zeng Genshui Wang 《Journal of Materials Science》2007,42(16):6917-6922
The heterogeneous precipitation method has been successfully used to prepare SrCO3 nanoparticle-coated BTO (BaCO3 or TiO2) powders by using PAA (polyacrylic acid) and NH4HCO3 as the dispersant and precipitator, respectively. Compared to the mixture obtained by the direct ball milling of the BaCO3, SrCO3 and TiO2 powders during the conventional solid-state process, this coated structure is effective for the low temperature synthesis
of barium strontium titanate (BST) powders. Sintering study of the powder synthesized by this method showed the dense and
fine-grained BST ceramics could be obtained at a low sintering temperature. The grain size effect on the sensitivity of the
dielectric constant vs. frequencies was discussed for the first time. Compared to the coarse-grained material, the fine-grained
sample exhibits the better sensitivity of dielectric constant vs. frequency at ferroelectric state. It was shown that as the
grain size decreased, the transition became diffuse, transition temperature (T
c) decreased and the dielectric constant increased. 相似文献